The objective of this proposal is to define the immunoregulatory role of human gangliosides. The studies are designed to determine the role of gangliosides in the immunosuppression frequently associated with cancer. Tumor cell gangliosides will be isolated and tested initially for inhibitory effects in the lymphocyte blastogenesis assay. The mechanism of the expected effect will be studied. Finally, the in vivo significance of these findings will be assessed in an animal model.